Arrays of acoustic transducers for physical analysis of batteries

ABSTRACT

Systems and methods for analyzing physical characteristics of a battery include arrangements of two or more transducers coupled to the battery. A control module controls one or more of the two or more transducers to transmit acoustic signals through at least a portion of the battery, and one or more of the two or more transducers to receive response acoustic signals. Distribution of physical properties of the battery is determined based at least on the transmitted acoustic signals and the response acoustic signals.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application for patent claims the benefit of ProvisionalPatent Application No. 62/416,506 entitled “ARRAYS OF ACOUSTICTRANSDUCERS FOR PHYSICAL ANALYSIS OF BATTERIES” filed Nov. 2, 2016,pending, and assigned to the assignee hereof and hereby expresslyincorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with U.S. Federal Government support under GrantNo. SBIR 1621926 awarded by the National Science Foundation. The U.S.Federal Government has certain rights in the invention.

FIELD OF DISCLOSURE

Disclosed aspects are directed to battery diagnostics. Morespecifically, exemplary aspects are directed to arrangements of sensorsfor use in physical analysis of one or more types and/or shapes ofbatteries.

BACKGROUND

The battery industry currently lacks an accurate, scalable method fordirectly measuring and monitoring the physical properties of batteriesbefore, during, and after use. X-ray and photon sources used in batterydiagnostics may be accurate but are expensive, and are not suitable forcommercial installations. Electrical methods for battery diagnostics maybe cheap and fast, which is why they are commonly used, but suchelectrical methods may provide inaccurate information about the internalcomponents of batteries such as the various electrode layers, separationmembranes, electrolyte, binder, etc. Physical properties of theseinternal components may change over time and use, and may degrade,particularly for batteries employed as a secondary battery. As such,there is a strong technological need in the art for the ability toanalyze, measure, and monitor differences and changes in the physicalproperties of batteries, wherein the batteries may be employed incommercial settings or for personal use.

During operation, all batteries depend on the transport of chargedspecies, though the mechanism of transport may vary depending on thetype of the battery. Some modes of transport include electronicconduction, ionic conduction, diffusion, and flow or convection. Asignificant proportion of batteries are constructed with tabs forelectrical connection to an external circuit. The placement of thesetabs influences the spatial distribution of the properties of interestwithin a given battery, depending on the geometry of the battery.

For example, with reference to FIG. 1, various types of batteries areshown. In batteries of the type, cylindrical cell 102, the distributionsof properties of interest therein are generally in the axial, radial, orthru directions or areal (i.e., combinations of directions); inbatteries of the pouch, prismatic, or other rectangular cells 104, thedistributions are lateral or areal; batteries of the type, coin orbutton cell 106, the distributions are generally in areal or in the thrudirection.

While the electrical methods widely used in the battery industry atpresent are not capable of accurately recognizing and analyzing thesespatial distributions in the physical properties of internal batterycomponents, there has been some recent effort demonstrating the use ofacoustic analysis to directly measure these properties. It has beenshown that the acoustic responses of primary and secondary batterieschange in repeatable and robust patterns that are unique to thechemistry and geometry of the batteries. Nevertheless, these analyseshave been limited to either a single-point approach, in which a singletransducer is used to send the input acoustic signal into the batteryand also to measure acoustic response (also referred to as “pulse/echo”or “reflection” mode), or a single-pair approach, in which onetransducer is used to send the input acoustic signal into the batteryand another transducer is used to measure the acoustic response (alsoreferred to as “transmission” or “through” mode). Neither approach isfully able to detect the distribution in physical properties.

In order to fully-resolve the spatial distribution in physicalproperties, there is accordingly a need for systems and techniques thatare able to make measurements at multiple points along the cell.

SUMMARY

Exemplary aspects of this disclosure are directed to systems and methodsfor analyzing physical characteristics of a battery, includingarrangements of multiple transducers configured to capture thedistributions in physical properties of batteries.

For example, an exemplary aspect is directed to an apparatus comprisingan arrangement of two or more transducers coupled to a battery. Theapparatus comprises a control module configured to control one or moreof the two or more transducers to transmit acoustic signals through atleast a portion of the battery, and one or more of the two or moretransducers to receive response acoustic signals, and an analyzerconfigured to determine a distribution of physical properties of thebattery based on the transmitted acoustic signals and the responseacoustic signals.

Another exemplary aspect is directed to an apparatus comprising anarrangement of two or more means for transmitting acoustic signalsthrough at least a portion of a battery, and one or more means forreceiving response signals based on the acoustic signals transmittedthrough at least the portion of the battery. The apparatus furthercomprises means for determining a distribution of physical properties ofthe battery based at least in part on the transmitted acoustic signalsand response signals.

Yet another exemplary aspect is directed to a method of analyzingphysical characteristics of a battery, the method comprising coupling anarrangement of two or more transducers to a battery, transmittingacoustic signals from the two or more transducers through at least aportion of the battery, receiving response acoustic signals to thetransmitted acoustic signals by one or more of the two or moretransducers, and determining a distribution of physical properties ofthe battery based on analyzing the transmitted acoustic signals and theresponse acoustic signals.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are presented to aid in the description ofvarious aspects of the invention and are provided solely forillustration and not limitation.

FIG. 1 illustrates different spatial distributions of potentialproperties of interest within a given cell.

FIGS. 2A-2B illustrate example arrangements of an array of acoustictransducers.

FIG. 2C illustrates an example apparatus comprising the examplearrangements of FIG. 2A.

FIGS. 3A-3B illustrate other example arrangements of an array ofacoustic transducers.

FIG. 4 illustrates examples of wavefronts generated based on controllingpulses of acoustic transducers disposed in example arrangements.

FIG. 5 illustrates an example 2D array of transducers for analyzingscattering behavior across a cross section of an example battery.

FIG. 6 illustrates an example process by which acoustic data andprevious knowledge about the structure of the battery are used tocalculate physical properties and reconstruct an image of an examplebattery.

FIGS. 7A-B, illustrate aspects of an example of process of FIG. 6applied to a battery comprising a cylindrical cell.

DETAILED DESCRIPTION

Aspects of the invention are disclosed in the following description andrelated drawings directed to specific aspects of the invention.Alternate aspects may be devised without departing from the scope of theinvention. Additionally, well-known elements of the invention will notbe described in detail or will be omitted so as not to obscure therelevant details of the invention.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any aspect described herein as “exemplary”is not necessarily to be construed as preferred or advantageous overother aspects. Likewise, the term “aspects of the invention” does notrequire that all aspects of the invention include the discussed feature,advantage or mode of operation.

The terminology used herein is for the purpose of describing particularaspects only and is not intended to be limiting of aspects of theinvention. As used herein, the singular forms “a,” “an,” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises”, “comprising,” “includes,” and/or “including,” when usedherein, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Further, many aspects are described in terms of sequences of actions tobe performed by, for example, elements of a computing device. It will berecognized that various actions described herein can be performed byspecific circuits (e.g., application specific integrated circuits(ASICs)), by program instructions being executed by one or moreprocessors, or by a combination of both. Additionally, these sequence ofactions described herein can be considered to be embodied entirelywithin any form of computer-readable storage medium having storedtherein a corresponding set of computer instructions that upon executionwould cause an associated processor to perform the functionalitydescribed herein. Thus, the various aspects of the invention may beembodied in a number of different forms, all of which have beencontemplated to be within the scope of the claimed subject matter. Inaddition, for each of the aspects described herein, the correspondingform of any such aspects may be described herein as, for example, “logicconfigured to” perform the described action.

Exemplary aspects of this disclosure are directed to arrangements ofmultiple transducers configured to capture the distributions in physicalproperties of batteries, which overcome the shortcomings of theconventional approaches discussed previously. Although reference is madeto batteries under test or subject to analysis using the exemplaryarrangements, it will be understood that the term “battery” is used toconvey any type of electrochemical energy storage device whose physicalproperties are to be analyzed using exemplary acoustic-signal basedtechniques. Thus, the term battery may convey a single battery cell or acombination (e.g., a string) of battery cells, a battery module, abattery pack, etc., without deviating from the scope of this disclosure.

In an aspect, the arrangements include arrays of two or more transducersconfigured for analysis of physical properties, and more specifically insome aspects, studying the distribution of physical properties of abattery. Acoustic transducers may be configured to convert variations inelectrical voltage into mechanical pressure or mechanical actuation, orvice versa. Thus, acoustic transducers may be configured to transmitacoustic signals through batteries or portions thereof. The transmittedacoustic signals or acoustic signals generated in response to theacoustic signals transmitted through the batteries or portions thereofmay be received by one or more transducers (e.g., the same or differentacoustic transducer which transmitted the acoustic signals), or inexemplary aspects, by other means for measuring vibrations such as oneor more accelerometers, optical or laser-based sensors, etc., withoutdeparting from the scope of this disclosure.

Accordingly, acoustic transducers (or simply, transducers), possibly inconjunction with other means for sensing vibrations (e.g.,accelerometers) may be used in performing analysis of batteries. Forexample, the analysis may be based on determining time of flight ofacoustic signals transmitted through batteries or portions thereof andcorresponding response signals received. For instance, acoustic signalbased techniques may be utilized in electrochemical-acoustic signalinterrogation (EASI) of the battery based on transmitting and receivingacoustic signals through at least a portion of the battery and studyingcharacteristics of the transmitted and received signals.

Example physical properties of batteries under test that may be ofinterest in this disclosure include, but are not limited to, thedensity, thickness, porosity, tortuosity, or stiffness of individuallayers or collections of layers within a battery; the viscosity, amountof or degree of wetting, or decomposition of the electrolyte; theformation of new layers within the battery; internal temperature;localized state of charge and state of health (or degradation thereof);local current density and electrochemical reaction rate, or combinationsthereof. These properties, and their distributions within a battery,evolve during operation and influence the performance of the batteries.

With reference to FIGS. 2A-B, example arrangements of transducers (e.g.,acoustic transducers for EASI, accelerometers for vibratorymeasurements, etc.) configured to transmit/receive acoustic signalsthrough/from at least portions of a battery. Accordingly, arrangementsof two or more transducers, e.g., in the form of arrays, may be used tostudy distribution of physical properties of the batteries.

For example, as shown in FIG. 2A, arrangement 200 comprises a lineararray of two or more transducers placed side-by-side, e.g., in asubstantially straight line (keeping in mind that the transducers neednot be tightly spaced or in contact with one another but may be sparselyspaced with a distance between one another while falling in a straightline arrangement). Arrangement 200 may be used to capture axial changes(e.g., any of the surfaces of a rectangular battery such as battery 104or axial surfaces of battery 102).

For instance, referring to FIG. 2C, an example system 250 for batteryanalysis using the exemplary arrangement 200 of transducers is shown.System 250 may include battery 252, which may be any type of batteryunder test. Arrangement 200 of transducers, e.g., in a linear array maybe coupled to battery 252. The transducers of arrangement 200 may becoupled to a control module such as ultrasonic pulser/receiver 256,which may be configured to control individual ones of transducers ofarrangement 200 to transmit pulses (at selected time instances and ofselected magnitudes), and to receive responses to the transmittedpulses. Although not separately shown, a computer or processing means,generally referred to as an analyzer, may be coupled to or providedwithin ultrasonic pulser/receiver 256 for analyzing the datacorresponding to the transmitted/received pulses and to determinedistributions of physical properties of battery 252 based on this data.Battery cycler 254 is also shown, which may be coupled to leads or tabsof battery 252 and configured to control charge/discharge cycles ofbattery 252. In some aspects, studying the physical properties ofbattery 252 during different states of charge may reveal usefulinformation pertaining to battery 252 and as such, battery cycler 254may cooperate with the remaining components of system 250 accordingly.

FIG. 2B shows another example arrangement of transducers, arrangement220, comprising a curvilinear array (which may be designed in concave orconvex depending on specific needs) of two or more transducers placedside-by-side to form a curved shape (once again keeping in mind that thetransducers need not be tightly spaced or in contact with one anotherbut may be sparsely spaced with a distance between one another whilefalling in a curved shape arrangement). Arrangement 220 may be used tocapture radial changes in battery physical properties, for example(e.g., they may be used on radial surface of battery 102 using a similarsetup as system 250).

In exemplary aspects, the arrays of transducers need not be limited to aone-dimensional (1D) array. For example, as shown in FIGS. 3A-3B,according to other designs, transducers may also be arranged,two-dimensional (2D) arrays 300 and 320, which may be of any regular 2Dshape, such as a rectangular, square, circle, ellipse, etc., or otherirregular 2D shapes as well, without departing from the scope of thisdisclosure. Arrays 300-320, for example, may be configured to captureareal changes in physical properties (e.g., for battery 104, using asimilar setup as system 250). Accordingly, exemplary arrays oftransducers may be configured as a linear array or a curved array, basedon whether the shape of the array or direction of distribution isradial, through, axial, or areal.

Furthermore, two or more arrays of transducers, e.g., pairs oftransducer arrays (arranged in any of the above-described configurationsof FIGS. 2A-B, 3A-B, e.g., linear, curvilinear, any 2D shape, orotherwise) may be used to perform spatially-resolved pulse/echo-modemeasurements wherein the response acoustic signal is measured on thesame side of the battery as the input or transmitted acoustic signal; ortransmission-mode measurements, wherein the response acoustic signal ismeasured on a different side, e.g., opposite or across from the side ofthe battery that the input acoustic signal was transmitted from.

In exemplary aspects of this disclosure, the two or more transducersused in the various arrangements may be controlled as a group orcontrolled individually and independently depending on specific needs.For instance, for some types of analyses, each transducer of anexemplary array (e.g., according to configurations of FIGS. 2A-B, 3A-B)may be independently pulsed.

In an aspect, a single transducer can be pulsed (i.e., caused togenerate an acoustic signal pulse) with enough temporal separationbetween pulses generated from adjacent or surrounding transducers of anarray, such that a response signal received by a transducer of the arraydoes not suffer from interference or unintended influences by the pulsesfrom the adjacent transducers. It is also noted that if two or moretransducers are placed far enough apart from each other (and notnecessarily adjacent to each other in the array) such that two or morepulses respectively generated by the two or more transducers do notinterfere with one another, then those two or more transducers may bepulsed simultaneously.

with reference to FIG. 4, aspects of creating different wavefronts basedat least in part on adjusting relative pulse timing of two or moretransducers in an exemplary array (e.g., according to configurations ofFIGS. 2A-B, 3A-B deployed in setups such as system 250) are illustrated.Starting with wavefront 402, it is possible to configure two or moretransducers in an array (e.g., linear array 200) to be pulsed orgenerate pulses, respectively and representatively shown with referencenumerals 402 a-d simultaneously, so that the acoustic wavefront (atleast initially) is a synchronous beam, whose shape is conformal to theshape of the array (linear, in this case). It will be understood thatthe shape of wavefront 402 may not be synchronous during the entirety ofthe transmission of pulses 402 a-d through at least portions of abattery under test to which wavefront 402 is applied because pulses 402a-d may encounter non-uniform effects due to variations in physicalproperties of the battery over the course of their travel. For instance,local differences in properties such as particle size, electrodedensity, thickness, etc. may affect wavefront 402 as well as anyresponse acoustic signals generated as a result of the transmission ofwavefront 402 through the battery under test.

Referring to wavefronts 404-406, it is seen that respective pulses maybe staggered in predetermined patterns by controlling the pulsing oftransducers in the arrays to result in different wavefront shapes. Forinstance, the transducers in an array may be pulsed in quick successionso that the pulses interact with each other. Such an approach may bereferred to as a phased array. Depending on the sequence and timing ofthe pulses, a number of wavefronts such as wavefronts 404-408 may becreated. Wavefront 404 represents a focused beam in which the wavescaused by respective pulses 404 a-d may constructively interfere at apredetermined or specified point. Wavefront 406 represents a steeredbeam in which the waves of respective pulses 406 a-d travel in a desireddirection which diverges from the direction of the synchronous beam ofwavefront 402 caused by simultaneous pulsing discussed above. Wavefront408 represents a combination of wavefronts 404 and 406 wherein a steeredand focused beam may be created by timing pulses 408 a-d in a manner inwhich the position of the focal point of wavefront 404 may be moved.

In some exemplary aspects, cross-sections of a battery may be studied.For instance, the response from one or more pulses from a singletransducer may be detected by the other transducers in an exemplaryarray, which allows for an understanding of the scattering behavior andcan provide tomographic-like (e.g., X-ray tomography) information.

For example, with reference to FIG. 5, exemplary array 500 oftransducers is shown, wherein the transducers are arranged in a 2Drectangular shape, or more specifically, square shape. Array 500 may beconfigured to analyze scattering behavior with respect to a crosssection 506 of a battery. The battery itself may be of any shape orsize, and tabs 502 and 504 are identified merely for reference, withoutany associated inherent limitations to the arrangement shown. Array 500,as illustrated, comprises nine transducers, disposed in positionslabeled pos 1-9. Each of these transducers may be configured to transmitan input acoustic signal into cross section 506 the battery (e.g., in adirection into the page) and receive a response acoustic signal from anyone of the transmitted acoustic signals.

A sequence of tests may be performed to study (transmit Tx, response Rx)pairs of acoustic signals which are identified based on the position(pos 1-9) of the transmitting transducer and the position (pos 1-9) ofthe receiving transducer. These signal pairs are shown with the notation(Tx position, Rx position) corresponding to the transmitting transducerand receiving transducer's positions and are identified as (1, 1) to (9,9). By studying the signal pairs in the various elements of thesequence, scattering behavior of the signals pertaining to cross section506 may be understood. For instance, if transmit, receive signal pairsstudied for each of the transducers configured to transmit and receivethe signals (e.g., pairs (1,1), (2,2), . . . (9, 9)) may revealinformation pertaining to any inhomogeneity that may exist in crosssection 506 of the battery. Similarly, by studying the differences inthe received signal strength for different receiving transducers for thesame input signal from a transmitting transducer (e.g., pairs (1, 1),(1, 5), (1,9)), the changes which cause signal fading across the variousreceiving transducers separated from the transmitting transducer bydifferent distances may be studied. In this manner, various otherscattering behaviors of signals may be used to determine properties ofthe battery, e.g., at least within cross section 506.

It will be appreciated that aspects include various methods forperforming the processes, functions and/or algorithms disclosed herein.For example, in addition to spatially-deterministic information aboutthe acoustic response and physical properties of internal batterycomponents, the data gathered from such transducer arrays can beanalyzed with physical models and related algorithms to reconstructspatial and volumetric mappings of the physical properties of thebattery. Such an exemplary tomographic-like approach in the field ofbattery diagnostics may be used to enable an in-field, in-use, at-scalephysical analysis of batteries which is not known to be possible toachieve using conventional approaches.

With reference now to FIG. 6, an example process 600 by which theacoustic data and previous knowledge about the structure of the batterycan be used to calculate physical properties and reconstruct an image.The various steps or blocks of process 600 will now be explained ingreater detail.

Starting in step 602, acoustic measurements may be taken at variouspositions on a battery under test (e.g., as explained with reference toFIG. 5 above at various transmit, receive positions).

In step 604, an inversion model may be used, wherein aspects of thephysical structure and properties of the battery may be estimated orcalculated from the acoustic signals measured at the various positions.

In a corollary step 606, a forward model may be used to calculate theexpected response acoustic signals at the various points based on apreliminary physical structure and properties of the battery (e.g.,based on prior knowledge about a baseline or initial physical structureand properties of the battery).

In step 608, the outputs of the inversion model from step 604 and theforward model from step 606 may both be studied, e.g., compared to oneanother in an effort to converge the two models. For instance the twomodels may be re-run with updated parameters obtained from thecomparison and the two models may be rerun in an iterative manner untilthe models converge (e.g., a set of parameters used to define the twomodels are determined wherein the set of parameters satisfy both theinversion model and the forward model).

In step 610, upon both models being satisfied, the physical structuresof the battery calculated at each measurement position may bereconstructed digitally to obtain a digital image of the battery.

With reference to FIGS. 7A-B, aspects of an example of process 600applied to battery 706 comprising a cylindrical cell is shown. In FIG.7A, various transducers, generally identified by the reference numeral702 are shown to be disposed in an example curvilinear arrangementaround a cross sectional area of battery 702, are illustrated.Transducers 702 may be configured to transmit and/or receive acousticsignals according to this disclosure and measurements from these may beused to analyze to reconstruct structural images of battery 702 usingprocess 600. Also shown are tabs, such as tab 704 of battery 706. Thelocation of these tabs may be determined by the above approach.

In FIG. 7B, transmission time of flight pertaining to acoustic signalsis plotted on the Y-axis with corresponding transducers 702 shown on theX-axis, identified by their rotational position on battery 706 of FIG.7A. The transmission times and intensities of acoustic signals shown inFIG. 7B reveal a rotational tomography of battery 706. The signalintensities are seen to fade at the position where tabs such as tab 704are present. In this manner, tabs or any other defects, deformities, orinhomogeneity in battery 706 may be detected.

Those of skill in the art will appreciate that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Accordingly, an aspect of the invention can include a computer-readablemedia embodying a method for analyzing a battery using exemplaryarrangements of transducers. Accordingly, the invention is not limitedto illustrated examples and any means for performing the functionalitydescribed herein are included in aspects of the invention.

While the foregoing disclosure shows illustrative aspects of theinvention, it should be noted that various changes and modificationscould be made herein without departing from the scope of the inventionas defined by the appended claims. The functions, steps and/or actionsof the method claims in accordance with the aspects of the inventiondescribed herein need not be performed in any particular order.Furthermore, although elements of the invention may be described orclaimed in the singular, the plural is contemplated unless limitation tothe singular is explicitly stated.

What is claimed is:
 1. An apparatus comprising: an arrangement of two ormore transducers coupled to a battery; a control module configured tocontrol one or more of the two or more transducers to transmit acousticsignals through at least a portion of the battery, and one or more ofthe two or more transducers to receive response acoustic signals; and ananalyzer configured to determine a distribution of physical propertiesof the battery based on the transmitted acoustic signals and theresponse acoustic signals.
 2. The apparatus of claim 1, wherein thearrangement comprises an array of the two or more transducers, wherein ashape of the array is based on a surface of the battery that thearrangement of the two or more transducers are coupled to or a directionof the distribution of the physical properties.
 3. The apparatus ofclaim 2, wherein the array is a linear array or a curved array, based onwhether the shape or direction is radial, through, axial, or areal. 4.The apparatus of claim 2, wherein the array is one-dimensional ortwo-dimensional.
 5. The apparatus of claim 1, wherein a distance betweentwo or more transducers in the arrangement of two or more transducers isbased on a tightly spaced arrangement or a sparsely spaced arrangement.6. The apparatus of claim 1, wherein the control module is configured tocontrol relative timing between two or more pulses transmitted throughtwo or more transducers based on a desired shape of a wavefront to beformed by the two or more pulses.
 7. The apparatus of claim 6, whereinthe control module is configured to transmit the two or more pulsessimultaneously to generate the wavefront, wherein the desired shape ofthe wavefront is a synchronous beam.
 8. The apparatus of claim 6,wherein the control module is configured to transmit the two or morepulses in sequence to generate the wavefront, wherein the desired shapeof the wavefront is one of a focused beam, steered beam, or a focusedand steered beam.
 9. The apparatus of claim 1, wherein the physicalproperties include on or more of: density, thickness, porosity,tortuosity, or stiffness of individual layers or collections of layerswithin a battery; viscosity, amount of or degree of wetting, ordecomposition of an electrolyte of the battery; formation of new layerswithin the battery; internal temperature; localized state of charge,state of health or state of degradation of the battery; local currentdensity and electrochemical reaction rate of the battery; orcombinations thereof
 10. The apparatus of claim 1, further comprising anarrangement of one or more accelerometers coupled to the battery, theone or more accelerometers configured to receive response acousticsignals.
 11. The apparatus of claim 1, wherein the two or moretransducers are disposed at predetermined positions with respect to across section the battery, and wherein the analyzer is furtherconfigured to determine a scattering of the physical properties withrespect to the cross section of the battery based on relative positionsof one or more transducers configured to transmit the acoustic signalsand one or more transducers configured to receive the response acousticsignals.
 12. An apparatus comprising: an arrangement of: two or moremeans for transmitting acoustic signals through at least a portion of abattery; and one or more means for receiving response signals based onthe acoustic signals transmitted through at least the portion of thebattery; and means for determining a distribution of physical propertiesof the battery based at least in part on the transmitted acousticsignals and response signals.
 13. A method of analyzing physicalcharacteristics of a battery, the method comprising: coupling anarrangement of two or more transducers to a battery; transmittingacoustic signals from the two or more transducers through at least aportion of the battery; receiving response acoustic signals to thetransmitted acoustic signals by one or more of the two or moretransducers; and determining a distribution of physical properties ofthe battery based on analyzing the transmitted acoustic signals and theresponse acoustic signals.
 14. The method of claim 13, furthercomprising: determining an inversion model from the distribution ofphysical properties of the battery determined based on analyzing thetransmitted acoustic signals and the response acoustic signals;determining a forward model comprising expected response acousticsignals for one or more transmitted acoustic signals based on apreliminary physical structure of the battery; comparing the inversionmodel and forward model to iteratively determine parameters whichsatisfy the forward model and the inversion model; and upon determiningparameters which satisfy the forward model and the inversion model,digitally reconstructing an image comprising physical properties of thebattery.
 15. The method of claim 13 comprising controlling relativetiming between two or more pulses transmitted through two or moretransducers based on a desired shape of a wavefront to be formed by thetwo or more pulses.
 16. The method of claim 15, comprising transmittingthe two or more pulses simultaneously to generate the wavefront, whereinthe desired shape of the wavefront is a synchronous beam.
 17. The methodof claim 15, comprising transmitting the two or more pulses in sequenceto generate the wavefront, wherein the desired shape of the wavefront isone of a focused beam, steered beam, or a focused and steered beam. 18.The method of claim 13, further comprising disposing the two or moretransducers at predetermined positions with respect to a cross sectionthe battery, and determining a scattering of physical properties acrossthe cross section of the battery based on relative positions of one ormore transducers configured to transmit the acoustic signals and one ormore transducers configured to receive the response acoustic signals.19. The method of claim 13, comprising arranging the two or moretransducers in an array, wherein a shape of the array is based on asurface of the battery that the arrangement of the two or moretransducers are coupled to or a direction of the distribution of thephysical properties.
 20. The method of claim 13, comprising configuringa distance between two or more transducers in the arrangement of two ormore transducers based on a tightly spaced arrangement or a sparselyspaced arrangement.